Anatomy 2: Ear

Question 1

Give 3 features of the Pterion

Answer 1

1) H-shaped suture
2) Consists of the frontal, parietal, temporal and sphenoid bone
3) THINNEST part of the skull

Question 2

What are the 2 parts of the temporal bone?

Answer 2

The squamous part

The petrous part

Question 3

What 2 bones make up the middle cranial fossa?

Answer 3

Sphenoid and temporal bone

Question 4

What part is the external ear?

What is the job in the external ear?

Answer 4

Auricle –tympanic membrane

Collects and conveys sounds waves to tympanic membrane

Question 5

What part is the middle ear?

What happens here?

Answer 5

Tympanic membrane – Oval window

Amplifies and conducts sound waves into internal ear

Question 6

What part is the internal ear?

What happens here?

Answer 6

Oval window -- internal acoustic meatus 
Converts special sensory info:
1) Into fluid waves 
2) Then action potentials 
3)Conducts APs to brain

Question 7

What is the general sensory nerve supply to the outer ear and describe its approx. whereabouts

Answer 7

C2,3 spinal nerve on the outside HELIX part

CNV3 + CNX in inner part towards tympanic membrane with CNVII mixed in !!

Question 8

What kind of cartilage is within the external ear?

Answer 8

Elastic

Question 9

Describe the sensory nerve supply in middle ear

Answer 9

Tympanic membrane is mostly CNV3

CNIX: Internal surface + Middle ear cavity + Eustachian tube + Nasopharynx + Oropharynx + Tonsils

Question 10

What are the 3 bones (in order of external -internal) within the middle ear cavity

Answer 10

Malleus // Incus // Stapes

Question 11

What do the 3 bones of the middle cavity join by?

Answer 11

Synovial joints

Question 12

What does the Eustachian tube connect?

Answer 12

The middle ear cavity to the nasopharynx

Question 13

How could earache mean you have tonsillitis?

Answer 13

The Eustachian tube & the nasopharynx have a shared nerve supply - CNIX

Question 14

How is the facial nerve involved within the middle ear cavity?

Answer 14

1) The chorda tympani (branch from CNVII) is present

2) CNVII innervates the right stapedius (reduces stapes movement so protects from very loud sounds)

Question 15

What does the chorda tympani do?

Answer 15

Parasympathetic supply to submandibular and sublingual glands

Question 16

What supplies the muscles of facial expression?

Answer 16

CNVII

Question 17

Describe the nerve supply to the internal ear

Answer 17

CNVIII - divided into 2 parts
The cochlear nerve (hearing)
The vestibular nerve (balance)

Question 18

What is the shell-like structure in the internal ear called? Where is it located?

Answer 18

The otic capsule
Located in the temporal bone
Swirly bit = ‘Cochlea’

Question 19

What is contained within the otic capsule?

Answer 19

Bony labyrinth which is fluid filled ('perilymph') 
Within the perilymph there is...
1) Membranous labyrinth 
2) Communicating sacs + ducts 
3) Ducts contain Endolymph fluid

Question 20

Describe the 7 steps of sound transmission

Answer 20

1) Sound waves make tympanic membrane vibrate
2) Vibrations transmitted through ossicles
3) Base of stapes vibrates in oval window
4) Vibration of stapes creates pressure waves in perilymph
5) Hair cells in the cochlea are moved, neurotransmitter is released, APs stimulated and conveyed to brain by cochlear nerve
6) Pressure waves descend and become vibrations again
7) Pressure waves are dampened at the round window